A LDPE (Low Density Polyethylene) factory consist of a 2-3 km tubular reactor, operating at high pressure (> 2500 bar) and rather high temperature (200-300°C). Raw material used in the process is ethylene and different additives. The tube is divided into zones in which oxygen compounds are injected to form free radicals and thereby initiate the polymerization.

The LDPE production process is constantly creating fouling. The fouling is a polyethylene layer with high molecular weight close to the wall which limits the cooling capacity and hence the reactor output.

The amount of fouling varies, and is somewhat controllable. For some of the equipment, the fouling is hard to measure in real time while running the process. Some kind of pointwise measurement from the outside of fouling built-up on the inside would be desirable, maybe by means of ultra sound. The temperature varies along the reactor, but is not more than 300°C and probably much less on the outside reactor tube surface.

Second, if possible, any anti-fouling coating applied on the inside of the reactor could be an alternative, with the material characteristics of; hard surface, erosion resistant and having a smooth surface.

We are of course also open for other ideas that can on-line measure, prevent and/or remove fouling. Ultra- sonic waves as a technique for prevent fouling to adhere on surfaces have been reported in the literature.